Conventionally, as a microelectromechanical system (MEMS) device, there has been proposed a device having provided within an encapsulation structure made of an insulation film such as a nitride film, a first electrode extended in a first direction on a semiconductor substrate, second electrodes arranged at both sides of the first electrode in a second direction orthogonal to the first electrode at a predetermined distance from the first electrode, a pair of pillars made of a conductive material provided at an end of each second electrode at a side of the first electrode, and a beam formed with a belt-shaped conductive material connecting the pair of pillars (see, for example, U.S. Pat. No. 6,936,494).
However, when a lateral oscillation or shock is given from outside to the MEMS device with such an encapsulation structure, a movable element such as the beam arranged within the encapsulation structure varies greatly, and has a risk of being damaged.